The present invention is directed to a method of manufacturing light waveguide branch elements and multi/demultiplexer elements, which elements operate in accordance with the beam dividing principle. The method includes providing a first body having a plurality of parallel extending light waveguides at a given spacing disposed along one side or surface thereof, cutting the first body into two sub-bodies or parts, polishing the cut surfaces, applying a reflective structure to one of the polished cut surfaces, reassembling the two parts into an assembly with the waveguide being axially aligned and the reflective structure disposed therein, providing a second body having a polished surface with parallel extending waveguides at said spacing and having polished end faces terminating in said polished surface, assembling the body on the assembly with the polished surface facing the one surface and the polished end faces of the second waveguides being in the proximity of the reflective structure to receive light reflected thereby, and securing the bodies in said assembled position to form the element so that the light traveling in the first waveguide is reflected by the reflective structure coupled into the ends of the second waveguide.
Methods are known for forming branch elements or multi/demultiplexer elements, which elements operate in accordance with the beam divider principle. Examples of these methods are disclosed in U.S. Pat. No. 4,339,290, which claims priority from German application No. 2,920,957, from copending U.S. patent application Ser. No. 246,100, filed Mar. 20, 1981, which claims priority from German application No. 3,012,184 and from an article from Applied Optics, Vol. 20, 1981, p. 3128. In the methods disclosed in these above mentioned references, the first body having a plurality of parallel extending waveguides on one surface is provided and so is a second body which has a plurality of waveguides whose end faces are terminated on a surface of the body. The second body is then assembled on the one surface of the first body with the waveguides of the second body being aligned with the waveguides of the first body and then the two bodies are joined together such as by cementing. The next method step is to produce a filter or mirror which occurs by cutting the assembled bodies along a plane extending at an angle of 45.degree. or 70.degree. relative to the axes of the fibers of the first body. The cut surface of one of the cut parts will also exhibit the light waveguide of the second body and must be very carefully ground and polished so that after applying a reflective structure, which can be either a partially reflective mirror or a wavelength selective filter, and the joining of the two parts back together, light traveling in the waveguides of the first body and reflected by the mirror will be coupled into the waveguides of the second body. The work step of positioning the cutting step and polishing the cut surfaces is very time-consuming and is critical. In many instances, improper polishing or over-polishing of the cut surfaces will render the branch elements defective.